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When did the Oligocene Epoch begin and end?

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Cenozoic migration routes — Cenozoic Era Principal Cenozoic faunal migration routes and barriers.

The Oligocene Epoch began 33.9 million years ago and ended 23 million years ago. It served as the third and final major division of the Paleogene Period, following the Eocene Epoch and preceding the Miocene Epoch of the Neogene Period.123